In 2006, Martin Casado, a student from Stanford University, led a project concerning network security and network management. By using a centralized controller, the project attempted to enable a network administrator to easily define security control policies that are based on a network flow, and apply these security control policies to various types of network devices, thereby implementing security control over the entire network communication. Inspired by this project, Martin and his advisor, Prof. Nick McKeown, found that: if the design is further generalized, that is, two functional modules, data forwarding (data plane) and routing control (control plane) of a traditional network device are separated from each other, and the centralized controller (Controller) is used to perform management and configuration for all types of network devices through a standardized interface, more possibilities can be brought for design, management, and use of network resources. Consequently, they proposed a concept of OpenFlow. Based on a programmable characteristic brought by OpenFlow for a network, Kate Greene further proposed a concept of a software defined network (Software Defined Network, SDN) during a selection of top ten cutting-edge technologies of the year 2009: If all network devices in a network are considered as managed resources, a concept of a network operating system (Network OS) may be abstracted by referring to a principle of an operating system. For one thing, this network operating system abstracts specific details of an underlying network device, and for another, provides a unified management view and programming interface for an upper-layer application. In this way, based on a platform of the network operating system, a user can develop a variety of application programs and use software to define a logical network topology, so as to meet different requirements on network resources, which does not need to consider a physical topology structure of an underlying network.
Therefore, an SDN/OpenFlow architecture is a new network architecture. Compared with IP route searching adopted in a traditional network, SDN/OpenFlow can implement flexible control over network traffic flow and provide a good platform for innovation of core networks and applications. SDN/OpenFlow is a direction of network architecture development in the future. However, the traditional network has the advantages of complete infrastructures and abundant resources. Therefore, research on the convergence of SDN/OpenFlow and the traditional network is of great significance.
However, as can be learned from the foregoing, it has been only several years up to now since SDN/OpenFlow emerged, and research on an SDN migration network (SDN Migration Network) that converges SDN/OpenFlow and the traditional network is far from sufficient. Therefore, up to now, how to ensure that a common user uses a traditional service normally while a VIP user is provided with an intelligent routing service of high quality and refined flow forwarding in the SDN migration network that converges SDN/OpenFlow and the traditional network has not been covered yet. That is, a network path is adjusted as required, so as to improve quality of service. It is defined in the present application that: a service that requires refined flow forwarding is referred to as an intelligent routing service, and a service that does not require refined flow forwarding is referred to as a common service. For example, a user originally watches a video in a common user manner, and now the user expects to upgrade to a VIP user, so as to obtain more bandwidth to ensure video smoothness, the user proposes an intelligent routing service request that requests reallocation of a flow forwarding network path with guaranteed quality for the user, so that the network path can ensure that the user has sufficient bandwidth for video watching.